Efficient Yatta Usage V1 (5_75)
By: GizmoTech-Mobile (A-L|Gizmo)
#Anime-Legion@irc.immortal-anime.net
YATTA is a wonderous tool used by a number of groups to achive high quality anime mpeg-4 encodes. It enables the user to perform a series of video clean up tasks, not limited to Inverse Telecine overriding, Freeze Frame assistance, Sectioned Filter application, etc...
The primary focus of YATTA is to perform IVTC (InVerseTeleCine). This is the act of correcting combing on the video source which matches "theorehtically" a 3:2 pull down pattern (ccnnc) and then removing on of the duplicate frames created by the "nc" match.
The secondary focus is on focused source improvements through a variety of means. The simplest involves back Freeze Framming, and moves into more intricate Sectioned Filtering. It also enables Variable Frame Rate manipulations with the end file being a VFR mkv file.
IVTC:
The main part of YATTA consists of the IVTC element. This is posibly the most important aspect and can be relatively time consuming. It has 2 key elements. The pattern component, and the threshold components.
Now you've already created your yap project (via ymc), and are ready to roll. The first step, if you've never dealt with the source in question before, would be to jump around the source and get a general idea of the VMetrics that you'll encounter. This is to acquire a VMetric number which will rest just above the peak normal scene value to allow smooth playback, but stop on critically wrong frames (scene changes, stray interlacing, chroma blending).
Once you've determined an appropriate value, place it into the VSearch window. Using abosolute value is usally the simplest way to go through the source, and the rest are for more specialized aplications. At this point you want to begin playing through the source. Your key viewing points are:
Mouth combs
Scene change combs (prior to)
Small movement combs
All of these are combs, which can be incorrectly matched by telecide naturally, and are what you need to visually pay attention to. The vsearch metric isn't going to stop the video on these frames, as they are generally very low as far as Vmetric is concerned (which is why they aren't matched correctly in the first place).
Now you will find it will also stop on frames which are non IVTC correctable via the switch interface, these situations are covered later.
IVTC Patern Matching:
So you're asking yourself, "Well Bludgers, how do I find a pattern in a scene"? There are really 2 easy ways to quickly find pattern. They involved tracking down an "NcccN" pattern.
First Method: Fast action
Identify a point in the scene (perferably near the start) where a hand/arm/body moves. Identify the first point of movement where it N matches, then set the next 3 frames C and hope that the next frame is a N match. Assuming all goes well, you've just identified a NcccN pattern, which, when moving to the next frame and Activating Auto Patern allows you to just play through the rest of the scene confident in knowing you've achived pattern.
Second Method: Mouth Transitions
The more dificult way, is to identify changes in mouth sizes. Alot of mouth transitions are done in frames of 5, which make identifying mouth transitions usually quite fast. Find a change where a mouth goes from big(er) to small(er) (or vice versa) and make sure it is an N match. Set the next 3 frames to C, and then the 4th frame, in theory, should be a N match on a nother transition. Assuming you were lucky and hit a NcccN pattern, you can now activate auto pattern and finish out the scene automatically.
Now an important point of note. In most cases a scene will NOT change pattern from start to finish, however there are rare occasions where the scene will change pattern mid stream.
Rest to come later.